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5439 |
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Thursday, June 08, 2017, Hall 28 11:20 AM Tribological Coatings |
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Practical experiences using HVOF-sprayed tungsten carbide coatings in the plastic foil industry |
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Kai Möhwald / Institut für Werkstoffkunde
Leibniz Universität Hannover, Germany Oliver Brandt* / Becon Technologies GmbH, Switzerland Wilfried Reimche/ Institut für Werkstoffkunde, Leibniz Universität Hannover, Germany Oliver Bruchwald/ Institut für Werkstoffkunde, Leibniz Universität Hannover, Germany Hans Jürgen Maier/ Institut für WerkstoffkundeLeibniz Universität Hannover, Germany |
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HVOF sprayed cermet coatings are in industrial use since the eighties. Among them coatings containing tungsten and chrome carbides were established as a standard. For these coating materials a wide range of powders with different particle-size distributions and combinations with different matrix metals are commercially available. For most applications powders with identical particle-size distributions and compositions are interchangeable, within the meaning that as long as the manufacturing process is identical other properties are nearly irrelevant. In plastic foil industry often complex strains occur on the surfaces of the used tools. These strains comprises from a chemical attack by means of released process gases due to the thermal conditions and from an abrasive component caused by additives of the plastic. Shaping calender rolls with a high gloss mirror finished surface may show only a minimal wear in such complex strains because otherwise the quality of the foil is affected in a negative way. In this range of applications the practical experience shows that with commercial characterization values such as microhardness and porosity HVOF sprayed tungsten carbide coatings are not sufficiently described. The article describes the effects of different microstructures on the application behaviour of a coating. For that purpose analytical methods such as quantitative phase analysis due to X-ray diffraction by means of Topas-Rietveld-Method were used. Preliminary results of the use of a novel eddy current test method suggest the potential to allow a local correlation of specific properties of the coatings with their microstructure. |